1. Field of the Invention
The present invention relates to a method of waterproof of an electric cable joint intended for waterproof and insulation of the joint, wherein the electric cable joint is received in a cap and a seal material is injected in the cap.
2. Related Art
FIGS. 7 and 8 show a conventional method of waterproof of electric cable joint described in the published patent application H10-243539 (pp. 3-4 and FIGS. 1-5) (JP, 10243539,A) referred to as Patent Document 1.
The method of waterproof of an electric cable joint constitutes the steps of injecting a sealing material 52 from above into a cap 51 made of synthetic resin standing, inserting a joint 54 of an electric cable 53 from above, fixing the electric cable 53 to an extension 55 of the cap 51 by a tape 56, and solidifying the sealing material 52 in an ambient atmosphere.
The joint 54 is formed by stripping an insulation cover of each end of a plurality of the electric cables 53 and exposing core wires (conductive portion) and connecting all together by heat press and the like.
The cap 51 has a semicircle bottom of vertical section and a cylinder of horizontal section with an opening 57 at one side. The cap 51 is made of synthetic resin such as polyvinyl chloride, polyethylene and polypropylene.
Various materials, such as urethane foam, hot melt material, various elastomer materials and the like are used as the sealing material 52. The sealing material 52 is of the character which flows at the time of injecting and solidifies when it is left. In order to solidify the sealing material 52 faster, a hardening agent is mixed to the sealing material. The sealing material 52 penetrates into the clearance of each electric cable 53 besides the joint 54 so as to prevent water from entering through the clearance among the electric cable 53 from outside.
The published patent application H10-243539 (JP, 10243539,A) describes that an annular portion is provided inside the cap 51 to hold the electric cable instead of the extension 55 of the cap 51 to hold the cable. This cap does not need a tape to hold and positions the electric cable 53 at the center of the cap.
The electric cable joint 54 is formed, for example, as one of a wiring harness of a vehicle and is used to apply a current with same electric potential to the plurality of electric cables 53 connected to electric components and auxiliary apparatus.
FIG. 9 shows a conventional cap for insulation of an electric cable joint described in the published patent application H08-22847 (JP, 822847,A) (pp. 3-4, FIG. 1).
A cap 61 is made of synthetic resin and is provided with a cap main body 62 with a bottom, and a flexible locking lance 63 disposed inside the cap main body. The flexible locking lance 63 is integrated to an opening 64 of the cap main body 62 through a thin hinge 65 and is folded back to receive the cap main body when the cap 61 is used. This structure makes a die cutting of the flexible locking lance 63 easy at the molding.
The joint 66 is prepared by the process that an insulation cover of each end of a plurality of electric cables 67 is stripped to expose a core wire and each core wire is pressure-bonded by a conductive metal sleeve.
The process of injecting a sealing material to the cap 61 is not described in the published patent application H8-22847 (JP, 822847,A). However, it is assumed that a waterproof sealing material 52 as in the document 1 is injected into the cap to obtain the waterproof of the joint 66.
However, at the conventional method of waterproof of an electric cable joint, when a sealing material is injected into a cap, air bubbles remain in the sealing material, especially in urethane foam. When the sealing material solidifies with the air bubbles remained, cracks or holes connecting the air bubbles easily occur and water penetrates into the sealing material through the cracks and holes resulting to the reduction of the waterproof and electric insulation of the electric cable joint.
If the viscosity of the sealing material is lowered to remove air bubbles quickly, the flow becomes high so that, when the joint is inserted into the cap, the sealing material spills over the cap opening and soils the cap, the curing time becomes longer and reduces the productivity.